Apple has completely sold out of the iPhone 3G across the U.S., according to Apple's online availability tool.
The 3G has been in extremely short supply and reports are that it is selling twice as fast as the original. Piper Jaffary analyst Gene Munster has previously estimated that the shortages could last for up to a month.
Meanwhile, AT&T continues to take backorders for the iPhone 3G and will deliver the units as they arrive.
Update: The tool appears to be inaccurate. You should call your local Apple Store to verify stock.